1. Field of the Invention
This invention relates to rotational coupling devices such as brakes and clutches and, in particular, to a fluid-actuated rotational coupling device in which fluid is provided from a shaft to the coupling through a sealed key.
2. Discussion of Related Art
Rotational coupling devices such as clutches and brakes are used to control transfer of torque between rotational bodies such as rotatable shafts. Conventional coupling devices can be actuated in a variety of ways including through electromagnetic actuation and fluid actuation. In fluid actuated devices, fluid may be provided to the device through hoses connected to fluid ports. Alternatively, fluid may be provided to the device through fluid passageways in a shaft on which the device is mounted. In the latter case, the fluid connection between the shaft and coupling device must be sealed. In conventional systems, grooves have been machined in the shaft or and device proximate the fluid connection to permit seals to be placed therein. Alternatively a pair of seals may be wrapped around the shaft on either side of the fluid connection. Because the seals must be periodically replaced, these conventional arrangements have several disadvantages. First, removal and replacement of the seals requires disassembly of the coupling device from the shaft. Second, the seals are subject to possible damage as the coupling device is installed on the shaft.
The inventor herein has recognized a need for a rotational coupling device that will minimize and/or eliminate one or more of the above-identified deficiencies.